The properties of the coating depend, among other things, on the preparation of the substrate surface and the spray parameters. One of the key properties of the coating is its adhesion to the substrate. Suitable preparation of the substrate surface has a great influence on the adhesion of the thermal spray coating. This work aims to study the influence of surface preparation on roughness of substrate and the resulting surface adhesion of coating. Another aim was to compare the effect of the chosen adhesion measurement method. A series of measurements of the roughness of the samples after grit blasting was performed. The effect of using new and used corundum was also taken into account. The selected coating for testing was TWAS (twin Wire Arc Spray) sprayed Zn15Al. The substrate material was low carbon steel 1.0570. The following adhesion measurement methods were chosen for the experiment - adhesion tensile test according to ASTM C633 - 79 standard, method using a special sample holder based on the ASTM C633 - 79 standard. In addition, a series of measurements were performed using Elcometer 510 Model T.

The cavitation performance of wear resistant cermet coatings can deteriorate in a corrosive environment. This investigation therefore considered the cavitation resistance in seawater of thermally sprayed High Velocity Oxy Fuel (HVOF) WC-10Co-4Cr coatings deposited on two different substrate materials of carbon steel and austenitic stainless steel. Coatings were deposited using industrially optimised parameters. Cavitation tests were conducted following the ASTM G32 test method in indirect mode, where there was a gap of 0.5 mm between the sonicator and the test surface. A submersed copper cooling coil controlled the temperature of the seawater. The cumulative cavitation erosion mass loss and cavitation erosion rate results are reported. The eroded substrate and coating surfaces were analysed using Scanning Electron Microscopy (SEM) in combination with energy dispersive x-ray analysis (EDX) to understand the failure modes. Coating phases were identified using x-ray diffraction. Results are discussed in terms of the cavitation failure modes and cavitation erosion rates for both the substrate and coated surfaces.

Cold spraying (CS) of high strength materials, e.g., Inconel 625 is still challenging due to the limited material deformability and thus high critical velocities. Further fine tuning and optimization of cold spray process parameters is required, to reach higher particle impact velocities as well as temperatures, while avoiding nozzle clogging. Only then, sufficiently high amounts of well-bonded particle-substrate and particle-particle interfaces can be achieved, assuring high cohesive strength and minimum amounts of porosities. In this study, Inconel 625 powder was cold sprayed on carbon steel substrates using N 2 as propellant gas under different refined spray parameter sets and powder sizes for a systematic evaluation. Coating microstructure, porosity, electrical conductivity, hardness, cohesive strength and residual stress were characterized in as-sprayed condition. Increasing the process gas temperature or pressure leads to low coating porosity of less than 1 % and higher electrical conductivity. The as-sprayed coatings show microstructures with highly deformed particles and well bonded internal boundaries. X-ray diffraction reveals that powder and deposits are present as γ- solid-solution phase without any precipitations. By work hardening and peening effects, the deposits show high microhardness and compressive residual stresses. With close to bulk material properties, the optimized deposits should fulfill criteria for industrial applications.

Laser cladding is a technology that uses high-energy-density lasers to quickly melt and solidify alloy powder on the surface of the metal substrate to form a cladding layer with good performance. Especially, martensitic stainless steel is widely used as a cladding material due to its high hardness and wear resistance. In this work, the martensitic stainless steel layers were fabricated on the C45 steel substrate by the laser cladding with different process parameters. The results show that holes in the cladding layer is unavoidable. The laser cladding process parameters have the important influence on the residual stress in the cladding layer. Under the action of residual stresses, the holes in the cladding layer will be the source of cracks, which will cause cracks in the cladding layer.

The aim of this study is to evaluate the effect of electromechanical treatment on the structure and wear behavior of plasma-sprayed nickel coatings. The coatings were air plasma sprayed on low carbon steel substrates, then electromechanically treated using different values of current density. Erosion resistance was assessed based on volume loss and coating microstructure and phase composition were evaluated via SEM and XRD. Erosion mechanisms were compared by analyzing coating cross-section and surface microstructures and wear resistance was associated with features such as defects, porosity, and cracks.

Cold spray has been proved to be a viable method for metallization of polymers and polymer composites. It has been reported that the mechanism of cold spray on polymeric substrates is different from the conventional mechanism on metallic substrates (i.e. adiabatic shear instability). In this work, single particle impact experiments were performed on polymeric substrates as well as mild steel. The particle-substrate interactions on different substrates were analyzed. Based on the results, the mechanism of cold spray on polymeric substrates is discussed and compared to that on metallic substrates.

The paper reports the results of structure examination of intermetallic Fe-Al type coatings obtained by the detonation gun spraying on a C45 plain carbon steel substrate. The structure was analysed with scanning (SEM), transmission (TEM) electron microscopy techniques and electron (SAE) and X-ray diffraction methods as well as quantitative inspection of composition in microareas (EDX). Special attention was paid to the interface between the coating and the substrate analyzing particularly the substructure of the individual grains contained up to 15μm away from the substrate surface layer. The results allowed explaining the formation mechanism of the coating morphology with a contribution of intermetallic phases Fe 3 Al, FeAl, FeAl 2 and Fe 2 Al 5 as well as the ε phase taking into consideration the influence of velocity, temperature and pressure on the powder particles during the D-gun spraying. It was established that the coating produced with the DGS method had sublayer morphology of alternate flattened and partially melted grains with wide range of Al content from 39 up to 63 at.%. Partial melting of the individual powder particles brought about the appearance of the amorphous grains and subsequently columnar crystals of the Fe-Al type phases formed sequentially at the interface area coating and cold substrate surface layer material, which was essential in the mechanism of the Fe- Al coating formation. It was established, that in the area of the polycrystalline dispersive structure formed from the highly plasticized FeAl grains during D-gun spraying, complex oxide films identified as Al 2 O 3 -γ formed, serving as specific composite reinforcement in the intermetallic Fe-Al coating. A mechanism of crystallization of partially melted Fe-Al particle containing nominally 63 at.% Al was carried out in the work in an attempt to explain the formation of different sub-layers within the Fe-Al intermetallic coating at the interface 045 steel surface layer.

A multi-layered thermal-sprayed coating system, developed as a resistive heating system, was deposited on a carbon steel pipe. The feasibility of using a 50Cr-50Ni coating as a heating element on top of a conductive substrate was studied. Alumina was deposited to serve as an electrically insulating layer between the metal coating and the substrate to restrict the flow of electrons from the metal alloy heating element to the steel substrate. Continuity, homogeneity, and adhesion of the coating were qualitatively analyzed by studying scanning electron microscope images. The performance of the heating system was determined by measuring the ice temperature and the times required to heat and melt the solid ice that was formed within the pipe. It was found that the coating system was able to generate the heat required to melt the ice in the pipe, thus avoiding the detrimental effects on the pipe of internal liquid freezing. This suggests that the proposed novel resistive heating system can be used on an industrial scale to mitigate or avoid the detrimental effects of ice accumulation in steel and other metallic pipes.

Previous results at McGill University have shown that metallic coatings can be successfully cold sprayed onto polymeric substrates. This paper studies the cold sprayability of various metal powders on different polymeric substrates. Five different substrates were used, including carbon fibre reinforced polymer (CFRP), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), polyethylenimine (PEI); mild steel was also used as a bench mark substrate. The CFRP used in this work has a thermosetting matrix, and the ABS, PEEK, and PEI are all thermoplastic polymers, with different glass transition temperatures as well as a number of distinct mechanical properties. Three metal powders, tin, copper and iron, were cold sprayed with both a low-pressure system and a high-pressure system at various conditions. In general, cold spray on the thermoplastic polymers rendered more positive results than the thermosetting polymers, due to the local thermal softening mechanism in the thermoplastics. Thick copper coatings were successfully deposited on PEEK and PEI.

In automotive industry, thermal spray process is used to reduce engine weight by replacing cast iron liners inserted in cylinder bores. Especially, twin wire arc spray is one of widely used thermal spray processes with inexpensive cost and high deposition rate. In this study, two kinds of wire materials, low carbon steel (0.07 wt.%C) and high carbon steel (0.80 wt.%C) were deposited by twin wire arc spray process using two kinds of process gas (i.e., compressed air and nitrogen) in order to elucidate effects of carbon contents of ferrous coating and process gas type on the hardness and wear resistance of coating. In case of hardness, low carbon steel coatings had higher hardness when air was used as process gas whereas high carbon steel coatings had higher hardness when nitrogen was used, which was caused by the counter effects of carbon loss and oxide formation. The results of sliding wear test in lubricated condition indicated that coatings with higher hardness have better wear resistance and oxides improve wear resistance by playing a role as solid lubricant. The main wear mechanism was splat delamination induced by inter-splat crack, and traces of other wear behaviours such as splat tip fracture and abrasive wear were also observed.

This work assesses the behavior of thermally sprayed corrosion-resistant alloy (CRA) coatings in an aqueous solution containing supercritical CO 2 . 316L stainless, Ti, alloy 625, and alloy C-276 powders were sprayed on carbon steel using a HVOF torch and 8 mm holidays were drilled in the coatings to expose the substrate. The samples were divided into two sets and placed in autoclaves for 30 days, where they were exposed to a salt solution, bubbled with 10 MPa CO 2 , at temperatures of 40 and 80 °C. Sample cross-sections showed that wherever the coating was intact, it protected the substrate from CO 2 corrosion, but in holiday regions, where bare steel was exposed, a siderite scale had formed and severe undercutting occurred, possibly due to galvanic interactions with the CRA coating.

In the present study, a new multi-chamber detonation sprayer (MCDS) was used to deposit Al 2 O 3 coatings on titanium and carbo steel substrates. SEM, TEM, and XRD analysis of the layer between the coating and substrate revealed the presence of an intermetallic compound that improves coating properties and is conducive to the relaxation of stresses generated during spraying.

Thermally sprayed aluminum (TSA) coatings have been successfully used to mitigate corrosion of carbon steel in offshore service, but concerns regarding its suitability in CO 2 -containing solutions have kept it out of the running for emerging carbon capture and storage applications. This paper presents the results of a 30-day test in which carbon steel specimens protected by TSA coatings were immersed in deionized water at ambient temperature in 0.1 MPa CO 2 . Acidity and corrosion potential were monitored during the test and dissolved Al 3+ ion content was analyzed at the completion. Based on experimental results, thermally sprayed aluminum is a viable candidate for corrosion mitigation in CO 2 -containing water as would be encountered in carbon capture and storage applications.

Commercially pure aluminum was arc sprayed on low-carbon manganese steel and electrochemical impedance spectroscopy (EIS) was carried on coating samples in a simulated marine immersion environment at 35 °C. A simple pore network circuit model was used to analyze the data and calculate the corrosion rate, which was estimated to be 5-15 μm/y from the charge transfer resistance value. After 9 months of exposure, the actual corrosion rate was found to be ~5 μm/y. The mechanism of protection offered by thermally sprayed aluminum (TSA) coatings is discussed.

This paper aims to clarify the development and characterization of cold-sprayed aluminum coatings on a non-regular medium-carbon steel surface. The work is carried out with a two-fold purpose: to optimize the deposition process and coating thickness and to learn how substrate defects and imperfections influence coating performance and the corrosion resistance of the coated material.

This paper presents research results showing how spraying distance affects the bonding strength, porosity, microhardness, and deposition efficiency of HVOF-sprayed NiCrAl coatings. The coatings examined were deposited on quenched 1045 steel substrates at spraying distances of 340, 360, and 380 mm. At the optimal standoff distance of 360 mm with kerosene and oxygen flow rates at 22 L/h and 850 L/min, respectively, NiCrAl coatings were achieved with a bonding strength of 66 MPa, microhardness of 418.56 HV 0.3 , porosity of 1.1%, and deposition efficiency of 65.3%.

Thermally sprayed aluminum (TSA) has been used in offshore applications for decades, protecting steel structures from seawater corrosion. However, very little work is reported on the performance of TSA when damaged, particularly in deep sea applications. This paper presents the results of a study in which an arc-sprayed aluminum-coated steel sample was subjected to synthetic seawater at 5 °C for 30 days in an autoclave at 50 MPa to simulate 5000 m of water pressure. Discontinuities or “holidays” amounting to 3% of the sample area were drilled into the coatings, exposing the underlying steel to direct attack by the synthetic seawater. After testing, SEM and EDX analysis revealed the formation of a protective Mg-based layer on the exposed steel with negligeable calcium content and no visible corrosion products. The results indicate that TSA coatings can protect steel in deep sea environments even when damaged.

This study investigates the use of cold gas spraying (CGS) for depositing braze filler coatings. In the experiments, pure Cu layers were sprayed onto Mg alloy substrates, which were then joined to AlSi steel by contact reaction brazing in a vacuum furnace. The bonding temperature influenced the dissolution of Cu as well as the eutectic reaction between the coating and substrate. The thickness of the brazed seam was found to be 300 μm although the initial thickness of the Cu layer was just 50 μm. The shear strength of the joint peaked at 37 MPa, corresponding to a brazing temperature of 530 °C. Intermetallic phases and interfacial defects of various types were responsible for the low strength of the joints.

This study demonstrates a new approach for producing thick copper coatings on steel by cold spraying via nitrogen gas. To overcome delamination problems without resorting to helium, substrate surfaces are treated prior to deposition using a forced-pulse waterjet. Samples with different levels of roughness were prepared using both conventional and waterjet surface treatments. The samples were then coated with thick Cu using only N 2 and adhesion tests were performed. Test results show good coating adhesion on all waterjet treated substrates with bond strengths ranging from approximately 25 MPa to 58 MPa, depending on surface roughness. Consistent with previous studies, cold spray Cu did not adhere to any substrates that had been polished or grit blasted. It is shown that the pulsed waterjet creates a surface with anchoring features that interlock with incoming particles to form a strong mechanical bond.

A low-cost, low-pressure (less than 1 MPa) cold spray unit was used to deposit tungsten carbide (WC)-based metal matrix composite (MMC) coatings on low carbon steel substrates. The coatings were then friction-stir processed (FSP) by using a flat cylindrical tool. Scanning electron microscopy (SEM), image analysis, micro-hardness testing, and ASTM Standard G65 dry abrasion wear testing were conducted to study the influence of FSP on the coating properties and its wear rate. It was found that porosity increased following FSP on the coating due to insufficient flow of the metal matrix material (nickel). The hardness of the WC-based MMC coating decreased after FSP as a result of increase in porosity and possible decarburization of the WC caused by the heat of the FSP. The SEM images taken from the cross sections of the FSPed coatings confirmed the effectiveness of FSP in distributing the WC particles within the matrix to produce a coating with uniform distribution of WC particles in the matrix. As a result, the abrasion wear resistance of the coatings after FSP increased compared to that of the as-sprayed coatings. This suggested that FSP can be considered as a method to improve the wear properties of MMC coatings.